Special railroad cars are used to transport vehicles such as automobiles and trucks from manufacturing plants to distribution centers. Such railroad cars are often referred to as auto rack cars. The number of decks which support the vehicles depends on the type of vehicles to be transported. Although some cars have a single deck it is more common to have two or three decks. Each deck will usually carry about four to six vehicles in the United States.
It is necessary to tie down or secure each vehicle to its supporting deck so that it remains in position while the railroad car moves from its point of loading to its destination. The system used to tie down each vehicle must be able to hold it securely even when the railroad car is subjected to buff and draft forces as well as when it rocks, rolls and bumps.
One of the ways widely used in the United States to tie down vehicles requires a pair of parallel tracks, spaced apart about forty inches outside, on each deck. The four wheels of each vehicle span the tracks and thus provide centering guides when the vehicles are driven onto the railroad car in column formation in so-called circus loading. After a vehicle is properly positioned on a deck it is pulled down tightly by use of four chains. Two chains are used at each end. Each chain free end is hooked to the vehicle frame or body adjacent the track. The chain extends downwardly to a carriage releasably slidable in the track and carrying a winch for tightening the chain. Such apparatus is disclosed in U.S. Pat. Nos. 3,566,803; 3,564,577; 3,374,008 and 3,673,969.
Although the described tie down apparatus has been successfully used for many years, recent vehicle structural changes have lowered road clearance, indicating that alternative systems should be used. Thus, it is no longer desirable to use a tie down system which pulls the body down and compresses the vehicle springs because this lowers the clearance between the vehicle underbody parts including mufflers, tailpipes and the like, and the deck. When the railroad car bumps and pitches, it can hit the deck and cause damage to the vehicle. Additionally, to withstand the tension applied to the underbody of the vehicle where the hooks are attached, special reinforcement must be added with increased cost solely to transport the vehicle and with no general benefit to the vehicle once it reaches its destination.
A further disadvantage of the prior art tie down system is that the laborer must have access to both sides of the vehicle; thus, space must be provided for him to work and walk on both sides. For some vehicles it is considered that tie down on one side only would be adequate if a suitable system is available. This would reduce the laborers time and lower costs.
Another disadvantage is that chains used to secure the vehicle essentially make inoperative the suspension system of the vehicle. This allows stresses imposed by rail shipment to be transmitted directly to the structure and mechanical parts of the vehicle.
From the above discussion it is believed clear that alternative tie down apparatus for vehicles transported by railroad car which eliminate some or all of the disadvantages of the prior art systems is needed.